Field of the Invention
The present invention relates generally to medical devices and methods. More specifically, the invention relates to devices and methods for partially and/or intermittently obstructing a pyloric valve to decrease gastric emptying, such as for treating obesity.
Obesity has become a medical problem of epidemic proportions in the United States. Recent governmental studies estimate that as many as 40% of Americans are obese (defined as a Body Mass Index over 30), and of those, almost 20% are morbidly obese. Unfortunately, there is no indication that these percentages will decrease and every indication that they will increase in the coming years. Studies have linked obesity to countless health risks, a small sampling of which includes cardiovascular disease, cancer, diabetes, orthopedic injuries and complaints, obstructive sleep apnea, chronic fatigue and depression. Despite billions of dollars spent searching for obesity cures, conducting research into nutrition and exercise, and educating the public about obesity, efforts to date have been largely ineffective.
Many Americans have tried combating obesity with diet, exercise and even medications, to no avail. Most people who lose weight through diet and exercise gain it back again in a short period of time. Available medications can have serious side effects, as was evidenced by the recent scare with the Fen-Phen dietary medication. Faced with the difficulty of diet and exercise, nutritional information that seems to change radically and rapidly, and diet medications and supplements that typically do not work and may cause serious side effects, many obese people become frustrated and either decide to remain obese or choose to pursue a more drastic treatment option.
The more drastic options typically involve surgical procedures, such as stomach stapling, other gastric reduction surgical techniques, placement of a constrictive band around the outside of the stomach, and gastric bypass. The most well known procedure, in part due to well-publicized experiences of celebrities like Al Roker and Carney Wilson, is the gastric bypass operation, known technically as a Roux-En-Y gastric bypass. In this procedure, the stomach is actually bypassed, and a very small stomach-like pouch remains, making a patient feel full after ingesting a small amount of food. Although gastric bypass can be highly effective, it is acknowledged to be a very high-risk operation, with a 1-2% mortality rate, a number of possible complications such as digestive problems, and a recovery period of up to 6 months. The other surgical alternatives are also associated with either high risk, low rate of effectiveness, or both.
Stemming from the high risks of gastric surgical procedures and the ineffectiveness of diet and exercise for many obese people, a number of medical devices have been developed to address weight loss and obesity, but these too have numerous drawbacks. Some devices, for example, try to bypass a portion of the stomach or small intestine by essentially creating a tube or chute through which food passes without any nutrients or calories being absorbed. Such devices are described, for example, in U.S. Pat. No. 5,820,584 and U.S. Patent Application Publication Nos. 2003/0040804 and 2003/0109931. Unfortunately, these are designed to cause absorption problems in a patient, which may reduce intake of calories into the body but which also typically leads to “dumping” of food too rapidly through the digestive tract, leading to numerous gastrointestinal symptoms.
Another approach, as described for example in U.S. Patent Application Publication No. 2003/0093117, involves performing a minimally invasive surgical procedure on a stomach, typically to reduce its volume. The drawbacks with such approaches are that they are still relatively invasive and they are typically difficult or impossible to reverse.
Other techniques involve placing space-occupying balloons and other devices within the stomach to make the patient feel full after eating small amounts of food. One such a device, for example, is described in U.S. Patent Application Publication No. 2003/0109935. Space occupying devices by themselves, however, may not be as effective as other treatments, and many currently available devices have an unacceptably serious risk of collapsing, passing through the stomach, and lodging somewhere in the intestines, thus causing a serious and potentially fatal intestinal blockage.
Yet another technique that has been attempted for treating obesity involves slowing down the rate at which food passes from the stomach, through the pyloric valve at the distal end of the stomach, and into the duodenum—i.e., the first part of the small intestine. Some researchers have found, for example, that stimulation of the gastric vagus nerve may result in reduced gastric motility leading to a loss of over 20% of excess weight in a nine month period. In another approach, severing the gastric vagus nerve may also be effective in treating obesity. These therapies, however, require invasive, sometimes irreversible, surgical procedures, and may have adverse effects on the ability of the vagus nerve to perform other important functions.
Others have tried slowing gastric emptying by placing implants or injecting bulking agents into tissue at or immediately adjacent the pyloric valve. Such techniques are described, for example, in U.S. Pat. No. 6,540,789 and U.S. Patent Application Publication Nos. 2003/0153806 and 2003/0158601. In general, such methods have not been found to be effective and, again, are often irreversible.
Therefore, because obesity is such an endemic and serious health problem, and because currently available treatment options are often ineffective, extremely risky or both, a need exists for effective, relatively non-invasive treatments for obesity. Ideally, such treatments would be relatively easy to use and deploy in a patient and would help treat obesity without a high risk of side effects or severe complications. Such treatments would also ideally be reversible. At least some of these objectives will be met by the present invention.